Re: Proposal: "Causal reads" mode for load balancing reads without stale data

 

Hmm, if that's where we're at, I'll summarize my thoughts.

All of this discussion presupposes we are distributing/load balancing queries so that reads and writes might occur on different nodes.

We need a good balancer. Any discussion of this that ignores the balancer component is only talking about half the solution. What we need to do is decide whether functionality should live in the balancer or the core. 

Your option (1) is viable, but only in certain cases. We could add support for some token/wait mechanism but as you say, this would require application changes not pooler changes.

Your option (2) is wider but also worse in some ways. It can be implemented in a pooler. 

Your option (3) doesn't excite me much. You've got a load of stuff that really should happen in a pooler. And at its core we have synchronous_commit = apply but with a timeout rather than a wait. So anyway, consider me nudged to finish my patch to provide capability for that by 1 Jan.